Unless someone creates an independent installer / upgrader package that will grab updates from unofficial sites, I.e. torrents. In which case the pirated versions are again almost the same as the registered versions. Then the only difference is the lag between the official and pirated versions, which is generally very low for popular products.

Convenience is the differentiator (itunes v.s. thepiratebay) and many consumers are willing to pay a premium for it.

Regardless, if you just accept that a good portion of your market won't pay for your product and work around it you can still have a very successful business. Then focusing on techniques like convenience, reward systems, free t-shirts? etc. can increase your paying customers. Maybe suing them can too, but it's definitely not the only way.